In 1991, S. Iijima (Nature, vol. 354 pp. 56-58) reported growth of multi-wall coaxial nanotubes, containing 2-50 layers with radial separations of about 0.34 nm, using an arc discharge evaporation method similar to that used for Fullerene synthesis. The nanotubes originally observed by Iijima were formed on the negative voltage end of an electrode pair and were plentiful in some regions and sparse in other regions. Since that time, other workers have developed other discharge means for controlled deposition of graphitic carbon. However, it is not straightforward to discriminate between, and control the growth and alignment of, a single wall carbon nanotube (“SWCNT”), a multi-wall carbon nanotube (“MWCNT”) and/or a carbon nanofiber (“CNF”).
The SWCNTs, MWCNTs and CNFs potentially have many applications that rely upon the large mechanical strength and/or large electrical or thermal conductivity associated with these structures, if the alignment of such structures can be controlled. Some workers have used liquid catalysts to initiate growth of some carbon nanotubes, but alignment of a finely detailed array of such structures is difficult or impossible using a liquid.
What is needed is a system and procedure that allows one to deposit an array of SWCNTs, an array of MWCNTs, or an array of CNFs, with increased alignment on a substrate, using a single electrode to define a growth direction. Preferably, the electrode should have an applied voltage in a range 0.1-100 Volts.